Method for recovering pyridine bases.



' FRAN K E. DODGE, OF NEW YORK, N. Y.,- AND FREDRICK H. RHODES, F PHILADELPHIA, PENNSYLVANIA, ASSIGNORS TOTHE BARRETT COMPANY, A CORPORATION OF NEW JERSEY.

METHOD FOR RECOVERING PYRIDINE BASES.

1,274,999 Specification of Letters Patent.

No Drawing. Application filed January 17, 1918. Serial No. 212,376.

To all-whom it"may concern:

Be it known that we, FRANK E. DODGE, of the city, county, and State of New York, and FREDRICK H. RHoDEs, of the city and county of Philadelphia, State of Pennsylvania,both citizens of the United States, have invented certain new and useful Improvements in Methods for Recovering Pyridine Bases, of which the'following is a true and exact description.

Qur invention relates to the recovery of the pyridine bases from the saturater bath liquor of the well known direct or semidirect ammonium sulfate processes, and has for its object the economical recovery of the pyridine bases, and incidentally the purification of the bath liquor.

lit is well known that in the manufacture of by-product coke and of illuminating gas some pyridine and pyridine homologues (as for example picoline, lutidine, quinoline, etc.) are formed. A portion of these bases, especially those of the higher boiling points, condense in the hydraulic mains and primary coolers, and are thus contained in the tar. A considerable portion of the lower boiling pyridine bases is, however, not condensed with the tar, but comes through the primary coolers and tar extractors as a component of the gas.

In the direct ammonium sulfate process and in the semi-direct ammonium sulfate process the gas from the tar extractors is eed from ammonia by passing through a saturated solution of ammonium sulfate, which solution is kept acid with from ten to six per cent. of free sulfuric acid. The ammonia in the gas is absorbed by this acid solution and crystallizes out from the bath liquor as ammonium sulfate, which is removed and recovered. The pyridine vapor .is also absorbed by the solution in the saturater bath, but only a negligible amount of pyridine or its compounds separates from' the bath until the concentration of pyridine in the tank reaches a certain minimum value of approximately 2% per cent. The contamination of the ammonium sulfate by pyridine depends not only on the amount of pyridine in the bath, but also upon the care taken in washing the ammonium salts and with careful washing the bath may be permitted to contain much more pyridine than 2% per cent. without loss of pyridine with the salt.

In our process we remove the bath liquor from a saturater bath which has been in use, preferably before the saturation of the bath liquor with pyradine bases has reached the point where the ammonium sulfate is contaminated by pyridine sulfates. We then pass ammonia or ammonia vapor into the bath, with the result that the ammonia first reacts with the free acid present to form ammonium sulfate. After most of the free acid is thus neutralized, the ammonia begins to react with the pyridine sulfate in the solution, forming ammonium sulfate, and setting free the pyridine bases. By saturating the bath solution with ammonia in this way, it is, we have found, possible to liberate all of the pyridine bases in the bath liquor.

Patented Aug. c, iota.

Having freed the pyridine bases in the" most all of the pyridine bases from the bath,

and from which the pyridine bases can be freed by well known processes, as, for instance, by a'gitating the oil with an acid.

Where, as is apt to be the case, distillates are driven off from the saturater tank by the heat of reaction, such distillates will contain a greater or less quantity of the pyridine bases, which must, of course, be condensed, and can be treated with an oil for the separation of the pyridine bases either alone or by retaining such condensates to the neutralized bath liquor and treating the distillates and the bath liquor together.

In our co-pending application for Letters Patent filed January 17, 1918, Serial Number 21237 5, we have described and claimed broadly the process of recovering the pyridine bases from the bath liquor of the direct or semi-direct ammonium sulfate processes by the neutralization of the bath liquor and consequent decomposition of the pyridine sulfates," and the subsequent recovery of the freed pyridine bases from such neutralized baths, describing and claiming also in said 00- ndin application an alternative met od -0 recovering the pyridine bases ent application is designed to cover specifically the claimed process in which the bath liquor is first neutralized, to decompose the pyridine sulfates, and is then treated for the recovery of the pyridine bases by agitation With an oil.

Having now described our invention, What We claim as new and desire to secure by Letters Patent, is:

The method of separating" the pyridine bases from the saturated baths of the direct or semi-direct ammonium sulfate processes which consists in saturating the bath liquor, consisting of a saturated acid solution of ammonium sulfate contaminated with salts of pyridine, with ammonia to liberate the pyridine bases from their combination with the acid of the bath and agitating the neutralized bath liquor with an oil to induce the absorption of the pyridine bases by the oil.

FRANK E. DODGE. FREDRICK H. RHQDES. 

